In recent years, as disclosed in PTL 1, a CMOS image pickup device, for example, for use in an imaging apparatus such as a digital camera may include an increased number of pixels because of miniaturization of pixels and are capable of capturing high-definition images. Recent imaging apparatuses for consumers may generally include 10 million pixels or more.
FIG. 18 is a configuration block diagram of such a general imaging apparatus. Referring to FIG. 18, an image pickup device 1500 includes a pixel part 1501, an AD conversion unit 1502, and a P/S conversion unit 1503. The pixel part 1501 converts a subject image to an electrical signal and outputs it to the AD conversion unit 1502.
The AD conversion unit 1502 converts an image signal read from the pixel part 1501 to a digital signal. The P/S conversion unit 1503 performs parallel-serial conversion on the digital signal converted by the AD conversion unit 1502. An image signal processing circuit 1600 performs a signal process on an image signal from the image pickup device 1500.
The imaging apparatus has a transfer path having a constant transfer capability for transferring an image data from the image pickup device 1500 to the image signal processing circuit 1600. Thus, an increased number of pixels in the image pickup device may relatively result in an increased transfer time of image data of a subject.
Also when the image size varies in accordance with each of image pickup modes, transferring image data of all pixels from the image pickup device 1500 to the image signal processing circuit 1600 may take time. In other words, the speed for transferring data from the image pickup device 1500 to the image signal processing circuit 1501 may be a bottleneck of the speed for reading out image data. Furthermore, such high speed transfer may increase the amount of power consumed and the amount of heat generated by the transfer circuit and the processing circuit, which may reduce the precision of the data transfer.
Accordingly, an image pickup device having a lower number of pixels may be required to be selected such that the data amount cannot exceed the transfer capability of a transfer path in a video recording at a higher frame rate. Because of this, achieving high definition video recording with a higher number of pixels may be difficult. Alternatively, in a case where an image pickup device having a higher number of pixels is used, data must be transferred from the image pickup device after the number of pixels to be read out from the pixel part is reduced by performing a thin-out process, for example.
Some imaging apparatuses may have an electronic zooming function for electronically zooming image in a target range from an imaging area while video recording is being performed and enlarging the size of the corresponding image. In the past, such an electronic zooming function is executed in the image signal processing circuit after image data of a reduced number of pixels are transferred from the image pickup device to an image signal processing circuit. Because of this, as the magnification of the electronic zooming increases, the rate of magnification of a target image increases, which may cause jaggy or degrade the sense of resolution.